Standard time sundial

ABSTRACT

A SUNDIAL COMPRISING A BASE ADAPTED TO BE VERTICALLY DISPOSED AND HAVING AN INCLINED MOUNTING SURFACE, A PIVOT MOUNTED ON SUCH SURFACE AND AN ARCUATE DIAL PLATE ROTATABLY MOUNTED ON THE PIVOT. A STYLE PLATE IS MOUNTED AT AN ANGLE TO THE SURFACE AND HAS TWO PARALLEL SHADOW CASTING EDGES, ONE FOR BEFORE NOON AND THE OTHER FOR AFTERNOON, SPACED BY A SELECTED DISTANCE SO THAT THE SHADOW OF AN EDGE UPON THE ARCUATE DIAL PLATE CAN INDICATE TIME. THE ARCUATE DIAL PLATE HAS APPROXIMATELY EQUALLY SPACED HOUR-MARKS GRADUATED ON A FIXED RADIUS FROM THE PIVOT. A &#34;LOCATION&#34; CORRECTION SCALE IS FIXED   TO THE SURFACE ADJACENT TO THE EDGE OF THE ARCURATE DIAL PLATE. THE DIAL PLATE HAS &#34;SEASON&#34; CORRECTION REFERENCE INDICIA FOR SELECTIVELY SETTING THE DIAL PLATE WITH RESPECT TO THE &#34;LOCATION&#34; CORRECTION SCALE.

1971 TOKUTARO YABASHI 3,616,533

I STANDARD TIME sunnun F1166. Junel 1968 2 Sheets-Sheet z mvErJmk,

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United States Patent 3,616,538 STANDARD TIME SUNDIAL Tokutaro Yabashi, 265 Akasaka-cho, Ogaki City, Japan Filed June 19, 1968, Ser. No. 738,334 Claims priority, application Japan, June 19, 1967, 42/ 52,545 Int. Cl. G04b 49/02 U.S. C]. 33-62 2 Claims ABSTRACT OF THE DISCLOSURE A sundial comprising a base adapted to be vertically disposed and having an inclined mounting surface, a pivot mounted on such surface and an arcuate dial plate rotatably mounted on the pivot. A style plate is mounted at an angle to the surface and has two parallel shadow casting edges, one for before noon and the other for afternoon, spaced by a selected distance so that the shadow of an edge upon the arcuate dial plate can indicate time. The arcuate dial plate has approximately equally spaced hour-marks graduated on a fixed radius fromthe pivot. A location correction scale is fixed to the surface adjacent to the edge of the arcurate dial plate. The dial plate has season correction reference indicia for selectively setting the dial plate with respect to the location" correction scale.

This invention relates to an improvement in south facing vertical sundials. The sundial of the present invention has a semicircular, nearly equally graduated dial and a very thick gnomon, which has two parallel styles widely spaced apart from each other. The graduation plate can be shifted around its center for the purpose of eliminating errors, depending on observers location and the season. The shadow of the style on the dial tells standard time directly.

In the following figures, same reference numbers designate same components in all the figures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a theoretical illustration of the graduations of the dial of this invention;

FIG. 2 is a front view of the sundial of this invention;

FIG. 3 is a perspective view of the dial in use showing the shadow indicating :30 am,

FIG. 4 is a side view of the dial partly in section through the dial pivot and a clearance hole in the dial.

The following explanation and FIG. 1 show an accurate method of laying out the hour marks for the new sundial. In FIG. 1, the lines O-12, 0-11, O-lO, O-9 which have been used from ancient times, are the morning hour lines for ordinary south vertical sundials in the latitude ,6". ,9 can vary within a wide range, but now, for convenience, the explanations will be made here for fi=.

The hour graduation angle a, is computed by the following formula tan a,=cos 45 tan t 1) where t, is the suns hour angle. The plotted values of a, are as follows:

3,616,538 Patented Nov. 2,, 1971 These hour lines, shown in Table 1 and FIG. 1, have unequal intervals. The invention contemplates a new method of laying out the hour marks M, P, Q, R, S, T and U which have nearly equal intervals. As in FIG. I, draw the line 60B from point 6 to a point B through 0 and draw the line BAF perpendicular to 60B from B. Draw the arc UM with radius l and center pivot at A. The arc UM cuts the hour lines O-6, O-7, O8, O9, (3-10, 0-11 and O-12 at U, T. S, R, Q, P and M respectively.

And then 4FAM=6 LFAP-=0 LFAQ=0 4FAR=0 0 :1 is generic and indicates the hour.

ice

FIG. 1 shows the relation between a, and 0 When a line is drawn perpendicular to OR, the 9 oclock line, at J from the center A.

AO=m, 4AOB=a AM=AP=AQ=AR =1: Radius of the arc 4MOP=a LMOQ=a 4MOH:a L'FAM'=912, LFAPZOJJ, LFAQ\=01U,

Then

m cos (a u)=l sin (0 a =AI In general:

in cos (a a)=l sin (0 a,) (2) By the trial and error method, from Formulas l and 2, 0, values were computed which have nearly arithmetically progressive values.

When OB:7.50 cm., BA=3.75 cm., l=16.77 cm., 6 has nearly equal differences as in Table 2.

*Meau value 1251 except 1255.

From Table 2 the differences between the angle of 0,, namely 1254.9', 1238.0', 1246.3, 1309 and 1254.7' are almost equal to one another except 126.6' (graduations from 6 to 7 am. are of little importance because they are used for a very short period), and the means 'value is 1251. The maximum deviation from the mean value is 13' and the ratio of the error to the mean value is less than 1.7%. For instance, when the difference between the solar time and the standard time is 25 minutes, the dial plate is shifted by an angle corresponding to 25 minutes around A; then the shadow of the style tells directly the standard time within an error less than about 25 seconds (25 minutes x 1.7% This error originates in the non-uniformity of the graduation. The extent of this error is permissible.

Therefore when a south facing vertical sundial is used in the latitude 45 N, it is very convenient to use the hour mark points M, P, Q, R instead of hour lines O -12, O-ll, O-10, 0-9 These hour points M, P, Q, R tell us 12, 11, 10, 9 oclock respectively.

Graduation for afternoon hours is made symmetrically to the line BAF on the right part of the dial plate 1 in FIG. 2 and FIG. 3.

In FIG. 2, the small graduation 12, attached to the dial plate 1, is a season" correction scale for the correction according to the equation of time (apparent time-mean time). The graduation 13, fixed on the base 4, is for the correction according to the observers location. These two graduations are divided by the mean value of the dial graduation.

The scales of 12 and 13 are graduated in such a way that one division of graduation 12 corresponds to 4 minutes in time of the season correction and that of graduation 13 corresponds to 1 of the location correction. Then, the angular distance around center A between two neighbouring graduations becomes 51.4.

With the aid of these two scales, the dial plate can be easily and quickly adjusted for the standard time.

FIG. 3 diagrammatically ShOlWS the dial when in use. The style plate 2 at OXX'O always makes an angle of 45 with the dial plate 1, because the graduation is for a south facing vertical sundial in the latitude 45 N.

As illustrative of other settings when the sundial is in the latitude 1/, suppose 1=35 N.

In FIG. 3, O is set parallel to the east-west horizontal line. The line 00' cuts the graduation at 6 a.m. and 6 pm. hour marks. A semicircular dial plate 1 of this sundial faces due south, and makes an angle with vertical line equal to Thus two edges OX and O-X' of the style 2 points to the celestial pole. O'Y, the shadow of OX, tells the solar time half past 10 oclock a.m. and in the afternoon the shadow of O'X' on the right part of the dial tells the afternoon solar time in the same Way.

In FIG. 2, graduation 13 is provided for places in Japan, near the longitude E. For instance, when the season correction is +8 minutes at a place of longitude E, near Tokyo, the main dial plate must be shifted around the center A to the position where the +8 minutes line in graduation 12 coincides with the 140 E line in graduation 13. Then the shadow of the style of the gnomon on the dial plate tells us the standard time in longitude 135 E, which is the Japanese Standard Time meridian.

As seen in FIG. 4, base 3 supports the dial, and surface 4 makes an angle with the vertical line equal to 10 (45=10 when p=35 N).

Side boards 15 and 16 and props 14 support the roof like style plate.

The pivot A of the graduation are, used to correct errors depending on the observers location and the season, is under the roof-like style plate of the gnomon and protected from nature.

As seen in FIG. 2 and FIG. 3, slots 7 and 9 are the guide grooves of the dial plate 1, and after correcting the errors, the dial plate is fixed by set screws 6 and 8. Apertures 10 and 11 are the windows or holes which allow the dial plate to rotate freely irrespective of the props 14 of the style plate 2.

If the correction is made on this dial, the dial can directly tell standard time very accurately between about 7 a.m. and 5 pm, while the sun shines upon the dial.

The error of the time, which the sundial shows, is negligibly small.

I claim:

1. A sundial comprising a base adapted to be vertically disposed and having an inclined mounting surface, a pivot mounted on said surface, an arcuate dial plate rotatably mounted on said pivot, a style plate mounted at an angle to said surface and having two parallel shadow casting edges, one for before noon and the other for afternoon, spaced by a selected distance so that the shadow of an edge upon said arcuate dial plate can indicate time, said arcuate dial plate having approximately equally spaced hour-marks graduated on a fixed radius from said point, and a location correction scale fixed to said surface adjacent to the edge of said arcuate dial plate, said dial plate having season correction reference indicia for selectively setting said dial plate with respect to said location correction scale.

2. A sundial as claimed in claim 1 in which a selected angular displacement of said dial plate around said pivot corresponds to a same time interval on the season" correction indicia, and the location correction scale.

References Cited UNITED STATES PATENTS 1,396,937 11/1921 Love 3362 A FOREIGN PATENTS 566,728 12/1932 Germany 3362 A 607,597 1/1935 Germany 33-62 A ROBERT B. HULL, Primary Examiner 

